Dissociation pathways of a series of alkali-cationized hybrid peptides, viz., Boc-alpha,beta- and -beta,alpha-carbopeptides, synthesized from C-linked carbo-beta3-amino acids [Caa (S)] and alpha-alanine (L-Ala), have been investigated by electrospray ionization tandem mass spectrometry. The positional isomers (six pairs) of the cationized alpha,beta- and beta,alpha-peptides can be differentiated by the collision-induced dissociation (CID) spectra of their [M + Cat-Boc + H]+ ions which give characteristic series of alkali-cationized C- (x(n)+, y(n)+, z(n)+) and N-terminal (a(n)+, b(n)+, c(n)+) ions. Another noteworthy difference is cationized beta,alpha-peptides eliminate a molecule of ammonia whereas this pathway is absent for alpha,beta-peptides. This is useful for identifying the presence of a beta-amino acid at the N-terminus. The CID spectra of [M + Cat-Boc + H]+ ions of these peptide acids show abundant rearrangement [b(n) + 17 + Cat]+ (n = 1 to n-1) ions which is diagnostic for distinguishing between alpha- and beta-amino acid at the C-terminus. MS(n) experiments of [b(n) + Li-H]+ ions from these hybrid peptides showed the loss of CO and 72 u giving rise to [a(n) + Li-H]+ and cationized nitrile product ions which render support to earlier proposals that b(n)+ or [b(n) + Cat-H]+ ions have protonated or cationized oxazolinone structures, respectively.
The 3‐amino‐6‐(trifluoromethyl)furo[2,3‐b]pyridine‐2‐carbohydrazide (5) was prepared from 3‐cyano‐6‐trifluoromethyl‐2(1H)pyridone (2) in series of steps via selective O‐alkylation, Thorpe–Ziegler cyclization followed by reaction with hydrazine hydrate. The 2‐carbohydrazide (5) was further reacted with aliphatic acids under different reaction temperatures to form a series of novel N‐acylfuro[2,3‐b]pyridine‐2‐carbohydrazide (6) and pyrido[3′,2′:4,5]furo[3,2‐d]pyrimidine derivatives (7). All the compounds 6 and 7 were screened for cytotoxic activity against breast carcinoma MD Anderson‐Metastatic Breast (MDA‐MB) 231 (aggressive) cell lines at 10 µM concentration. Compounds 6a, 6b, and 6c showed promising activity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.